Thermal barrier coatings for gas-turbine engine applications

Hundreds of different types of coatings are used to protect a variety of structural engineering materials from corrosion, wear, and erosion, and to provide lubrication and thermal insulation. Of all these, thermal barrier coatings (TBCs) have the most complex structure and must operate in the most demanding high-temperature environment of aircraft and industrial gas-turbine engines. TBCs, which comprise metal and ceramic multilayers, insulate turbine and combustor engine components from the hot gas stream, and improve the durability and energy efficiency of these engines. Improvements in TBCs will require a better understanding of the complex changes in their structure and properties that occur under operating conditions that lead to their failure. The structure, properties, and failure mechanisms of TBCs are herein reviewed, together with a discussion of current limitations and future opportunities.     

Environment. Sustainable development of the agricultural bio-economy

A U.S. farm policy shift to joint production of commodities and ecological services will advance sustainable agriculture.     

Strontium incorporation into dental enamel

Rats were raised on diets either rich or poor in strontium. Powder x-ray diffraction patterns suggest that isomorphous substitution of strontium for calcium occurs in the apatite of tooth enamel, and that strontium may form Sr(6)H(3)(PO(4)) * 2H(2)O, a compound hitherto unreported in biologic systems.     

Solid-Solid Interaction Studies by Spectral Reflectance

Spectral reflectance measurements show that the concept of the effect of solvents on the electronic absorption spectra of carbonyl compounds in various solvents as interpreted by polarization theory can be extended into model solid-solid systems, and that slow interaction between a powdered solid and an active adsorbent permits the detection of spectral changes which may be used for kinetic studies of the process of adsorption.     

Two distinct populations of calcium channels in a clonal line of pituitary cells

The whole-cell variant of the patch clamp technique was used to study calcium channels in GH3 cells. Two distinct populations of calcium channels, first recognized from their closing kinetics, were observed. The slowly closing channels are activated in a relatively negative voltage range and are inactivated within 100 milliseconds. They conduct barium and calcium about equally well. The fast closing channels are activated at more positive voltages, are not inactivated during a 100-millisecond pulse, conduct barium in preference to calcium, and are activated slightly more rapidly than the slowly closing channels.     

Size and age are important factors for marine sanctuaries: evidence from a decade of systematic sampling in a subtropical marine park

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